A research project is described which involves a systematic laboratory analysis of relationships between environmentally-controlled behavioral stress and the consumption of oxygen. Since oxygen consumption is directly related to total energy expenditure, measurements of this fundamental process may well provide a unique approach to the assessment of stressful interaction patterns involving organism and environment. Recent efforts have produced a functional system which allows a sensitive and continuous measure of O2 consumption in the baboon. Preliminary studies using these techniques in relationship to continuous measurement and control of selected behavioral performance have demonstrated the feasibility of a more extensive psychophysiological stress analysis. The objectives of such an experimental analysis would envision the establishment of definitive relationships between behavior and O2 consumption, on the one hand, and the exploration of energetic factors as they may be related to the valence of complex reinforcing events, the nature of stress, and ultimately to the emergence of a fundamental "economics" of behavior, on the other.